10-4 Solve It!
On a piece of grid paper, draw a 3 unit-by-4 unit rectangle. Then draw
three different rectangles, each similar to the original rectangle. Label
them I, II, and III. Use your drawings to complete a chart like this.
You know from
previous lessons
that if you
double the length
and width of a
rectangle, its area
is quadrupled.
Rectangle
Perimeter
Area
Q
Q
Q
Q
Q
Q
Q
Q
Original
I
II
III
Use the
the fi
firstt chart
like this.
h information
i f
ti from
f
th
h t tto complete
pl t a chart
h t lik
Rectangle
Scale
Factor
Ratio of
Perimeters
Ratio of
Areas
Q
Q
Q
Q
Q
Q
Q
Q
Q
I to Original
II to Original
III to Original
How do the ratios of perimeters and the ratios of areas compare with
the scale factors?
10-4 Lesson Quiz
1. The triangles below are similar. The ratio of the
4 in.
lengths of corresponding sides is 49 .
a. What is the ratio (smaller to larger) of
9 in.
the perimeters?
b. What is the ratio (smaller to larger) of
the areas?
2. Do you UNDERSTAND? Mr. Williams is building a sand box
hsm11gmse_1004_FPL2.indd 635
2/13/09 3:51:50 AM
for his children. It costs $228 for the sand if he builds a sand
box with dimensions 9 ft by 6 ft. How much will the sand cost
if Mr. Williams decides to increase the size to 1312 ft by 9 ft?
Answers
Solve It!
Check students’ tables. The
ratio of the perimeters is the
same as the scale factor;
the ratio of the areas is the
square of the scale factors.
Lesson Quiz
1. a. 4
9
2. $513
Prentice Hall Geometry • Solve It/Lesson Quiz on Transparencies
Copyright © by Pearson Education, Inc., or its affiliates. All Rights Reserved.
66
16
b. 81